444 MEANS OF DEFENCE OF INSECTS. 



The powers of annoyance by means of their hairs, with which the moth 

 of the fir, and the procession-moth, before noticed, are gifted, are doubtless 

 a defensive armor to them. Madame Merian has figured an enormous cater- 

 pillar of this kind, — which unfortunately she could not trace to the perfect 

 insect, — by the very touch of which her hands, she says, were inflamed, and 

 that the inflammation was succeeded by the most excruciating pain.^ The 

 vesicatory beetles, likewise (^Cantharis vesicatoria, &c.), are not improba- 

 bly defended from their assailants by the remarkable quality, so useful to 

 suffering mortals, that distinguishes them. 



Your own observation must have proved to you, that insects often 

 escape great perils, from the crush of the foot, or of superincumbent 

 weights, by the hardness of the substance that covers great numbers of 

 them. The elytra of many beetles of the genus Ulster are so nearly 

 impenetrable, tHat it is very difficult to make a pin pass through them ; 

 and the smaller stag-beetle (Tforcus j)aralle]ij)ipedus) will bear almost any 

 weight — the head and trunk formino- a slight angle with the abdomen — 

 which passes over it upon the ground. Other insects are protected by 

 the toughness of their skin. A remarkable instance of this is afforded 

 by the common forest-fly (Hippohosca equina^, which, as was before 

 observed, can scarcely be killed by the utmost pressure of the finger and 

 thumb. 



The involuntary secretions of these little beings may also be regarded 

 as means of defence, which either conceal them from their enemies, make 

 them more difficult to be attacked, or render them less palatable. Thus, 

 the white froth often observable upon rose-bushes, and other shrubs and 

 plants, called by the vulgar frog-spittle, — but which, if examined, will be 

 found to envelop the larva of a small hemipterous insect (Aphrophora 

 spumaria), from whose anus it exudes, although it is sometimes discovered 

 even in this concealment by the indefatigable wasps, and becomes their 

 prey, — serves to protect the insect, which soon dies when exposed, not 

 only from the heat of the sun and from violent rains, but also to hide it 

 from the birds and its other foes. The cottony secretion that transpires 

 through the skin of Eriosoma^, and some species of Coccus, and in which 

 the eggs of the latter are often involved, may perhaps be of use to them 

 in this view ; either concealing them — for they look rather like little locks 

 of cotton, or feathers, than any thing animated — or rendering them dis- 

 tasteful to creatures that would otherwise prey upon them. The same 

 remark may apply to the slimy caterpillars of some of the saw-flies (&- 

 landria Cerasi, Allantus Scrophularice, he). The coat of slime of these 

 animals, as Professor Peck observes^, retains its humidity though exposed 

 to the fiercest sun. Under this head I shall also mention the phosphoric 

 insects : the glow-worm (Lampyris) ; the lantern-fly (Fulgora) ; the fire- 

 fly (Elater) ; and the electric centipede {Geophilus electricus) ; since 

 the light emitted by these animals may defend them from the attack of 

 some enemies. Mr. Sheppard once noticed a Carabus running round the 

 last-mentioned insect, when shining, as if wishing but afraid to attack it. 



' Insect. Surinam, t. 57. Two different species of caterpilLirs apparently related to this 

 of Madame Merian were in the late Mr. Francillon's cabinet, and are now in my pos- 

 session. 



* To this genus belongs the apple Aphis, called A. lanigera, 



' Nat. Hist, of the Slug-worm^ 7. 



